A satellite navigation receiver must detect and acquire the precise orbit (ephemeris) data for at least four satellites before it can produce a 3-dimensional position solution. In cold-start sky-search mode, however, the satellite navigation receiver has no prior knowledge of what satellites are visible and not visible. Moreover, in this mode, the satellite navigation receiver generally will not have accurate time and position information, valid satellite ephemeris data, approximate satellite Doppler or code phase information. Searching for a satellite in cold-start mode thus requires searching all possible code phases (0-2045 half-chips) and all possible Doppler frequencies (+/−4,100 Hz +/− reference oscillator uncertainty). A typical satellite navigation receiver searches linearly for one or more satellites at a time, wherein the satellite search order is based on the satellite identification (SVID), for example, search for SV1, then SV2, SV3 and so on through the last satellite in the constellation. The period of time between starting the search for the first satellite and computation of an accurate position computation is called the time-to-first-fix (TTFF).
The various aspects, features and advantages of the disclosure will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description thereof with the accompanying drawings described below.